Method for the production of protein preparations with essentially constant properties with regard to solubility and functionality within a ph range from about ph 3 to ph 10

ABSTRACT

Disclosed is a method for producing protein preparations having essentially constant functional properties for technical applications within a broad pH range from about pH 3 to pH 10 by means of extraction from a starting product which contains protein, notably legumes, grains or oilseed. The invention is distinguished by the protein-containing starting product undergoing at least one liquid extraction step and that the raffinate and/or extract obtained thereby undergoes at least one membrane separation process in which a residue is obtained or undergoes thermal upgrading in which a concentrate is obtained and that the residue or the concentrate contain the protein preparations having the desired functional properties.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for the production ofprotein preparations with essentially constant properties with regard tosolubility and functionality within a broad pH range from about pH 3 topH 10 by means of extraction from a protein-containing starting product,notably legumes, grains and oilseeds. Furthermore, such a proteinpreparation and suited applications thereof are described.

BACKGROUND OF THE INVENTION

[0002] Proteins respectively protein preparations are considered as rawmaterials for the food and feed industries. They find much use inindustrial chemistry, for example in the production of adhesives,emulsions for photographic coats and cosmetics just to name a fewapplications.

[0003] The major significance of protein preparations for all livingthings, for products and materials of the entire food chain and for amultiplicity of products and materials for industrial applications arebased on the functional properties of the individual proteins, such asbeing water-bound or oil-bound, foam formation, moreover dispersion,solubility, gel formation, viscosity, emulsifiability andthermostability.

[0004] Depending on the type of proteins, their functional propertiesare different and change essentially in dependence of certainparameters, such as for example in dependence of the ambient temperatureor the pH value. Depending on the technical requirements, the functionalproperties of protein preparations can be selectively adjusted byselecting the external parameters, such as disclosed for example in DE197 21 079 A1. Thus, solubility, viscosity and other certain functionalproperties for technical applications can be selectively adjusted bymeans of corresponding selective thermal treatment.

[0005] In the industrial production of protein preparations based onvegetable proteins, of the legumes lupine seeds and peanuts, peas andsoybeans are of the greatest significance as a starting product comparedto all the other vegetable starting materials because legumes possessapproximately 40% protein. Oilseeds, for example poppy seeds, sesameseeds, coconuts, almonds, linseeds, rape seeds, sunflower seeds etc. aswell as wheat, corn, rye etc., are vegetable starting products forproducing protein preparations even if they contain less protein thanthe aforementioned legumes.

[0006] For large-scale production of protein preparations, in particularfor the production of protein isolates which have a protein content ofmore than 90% as dry substance, legumes such as soybeans or lupinesundergo multistage process steps.

[0007] First the proteins are extracted from the starting materials withthe aid of an alkaline aqueous solution after, if required, the startingmaterials had undergone a preceding acidic extraction. The extraction,which is carried out under alkaline conditions, is followed byprecipitation of the proteins under acidic conditions. Finally theproteins precipitated in this manner are dried and are then availablefor suited technical as well as food-related applications. A prior artmethod of production is, for example, disclosed in DE 198 13 207 C1.

[0008] The protein preparations produced with the prior art methods ofproduction respectively isolation possess, due to the method ofseparation utilized in their production, pH-value dependent solubilityproperties, which have a marked minimum in particular in the case ofacid pH values, i.e. in the case of pH values of <7 and in particular inthe case of pH values from 4 to 5, protein preparations produced in thismanner are poorly soluble in water respectively completely insoluble inwater.

[0009] The protein preparations produced with prior art methods behavein the same manner with regard to their functional properties, forexample with regard to emulsification and foam formation. Accordingly,the protein preparations emulsify significantly worse in an acid rangethan in a neutral respectively slightly alkaline range, i.e. the abilityto stabilize emulsions worsens considerably. Emulsifibility plays animportant role especially in the food and cosmetic industries, forexample in the production of dressings, sauces, mayonnaise or cosmeticproducts such as creams or salves and technical products such asadhesives, glues, rubber mixtures, etc.

[0010] For many applications, however, for example in the areas of foodproduction, cosmetics as well as in the area of technical products it isdesirable to use protein products whose functional properties arelargely independent of parameters such as, in particular, the pH value,ionic strength and/or temperature. Such type protein preparationscannot, however, be produced with the present methods of production, inparticular, not on a large industrial scale. Production methods forprotein preparations having these property profiles are based onmodifying the proteins, which occurs following protein production and isusually technically very complicated, such as is carried out, forexample, using hydrolytic enzymes.

SUMMARY OF THE INVENTION

[0011] The object of the present invention is to provide a method forproducing protein preparations with which the production of proteinpreparations is possible on an industrial scale, whose functionalproperties for technical applications, in particular, with regard toemulsification and foam formation, are largely independent of the pHvalue in the range between pH 3 and pH 10. Moreover, the proteinpreparations produced with the invented method should posses almostunchanged solubility properties in water even at temperatures up to 100°C. In particular, the protein preparations should have a wide spectrumof use so that they can be employed in many products with regard tofoodstuffs and technical products as well as cosmetic products.

[0012] The solution to the object on which the present invention isbased is set forth in claim 1. Alternative variants of the methodaccording to the present invention are put forth in claims 2, 5, 10 and13. A protein preparation according to the present invention is thesubject matter of claim 24. A claim directed at a preferred use is givenin claim 30. Advantageous features are the subject matter of thesubclaims and the entire description.

[0013] The starting product for the invented method for the productionof protein preparations having largely constant functional propertieswithin a broad pH range of about pH 3 to pH 10 are the as such knownlegumes or oilseeds. The invented method is based on an extractionhaving the following steps:

[0014] First the protein-containing starting product undergoes anaqueous extraction step. The obtained extract is then either subjectedto at least one membrane separation process in which a residue isobtained or undergoes thermal upgrading in which the concentrate isobtained. In both instances, whether it be the obtained residue or theobtained concentrate, protein preparations with the desired functionalproperties are obtained.

[0015] The new protein preparations produced in the aforedescribedmanner have a protein content between 60 and 95% as dry substance andpossess functional properties which are not achievable with the priorart methods: accordingly the new protein preparations possess highsolubility as well as resolubility in aqueous systems in a pH rangebetween 3 and 10. Furthermore, they possess thermostability in the samebroad pH range and retain their solubility even at temperatures from upto 100° C. In particular, the quality of foam formation andemulsifibility of the novel protein preparations proves to be almostconstant over a broad pH range between 3 and 10. Finally, they possess ahigh sulfurous amino acid content which is especially advantageous forphysiological nutritional reasons with regard to chemical modifiability.

[0016] The reason for such strikingly favorable behavior with regard totheir functional properties appears to be the relatively high content ofnonprecipitable globular protein fractions with a molecular weight ofapproximately 200,000 D in the produced protein preparations (inparticular produced from lupines). Alternative possible technicalproduction of such type protein preparations having a similarly highproportion of nonprecipitable globular protein fractions have hithertonot been known.

[0017] Analyses of the protein preparations produced from legumes, inparticular lupine seeds, using the invented method possess a highgamma-conglutinin content corresponding to a fraction which distinctlydiffers from all other protein preparations with regard to their aminoacid composition as well as solubility and pH-dependent solubility.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Described in the following are four alternative variants of themethod suited for the invented production of high-molecular proteinpreparations having the desired almost pH-value independent functionalproperties. Suited as the starting material for the to-be-obtainedprotein preparations are preferably comminuted, that is ground, flakedor pelletized lupine seeds, preferably produced from shelled lupines,such as for example L. albus, L. luteus, L. angustifolius, L. mutabilis.The comminuted lupine seeds may be faculatively deoiled in a preliminaryprocess, such as for example as disclosed in the German printedpublication DE 198 13 207 C1. As an alternative also suited as astarting material are soybeans, peas, grain and oilseeds.

[0019] Variant 1:

[0020] First the comminuted and facultively deoiled lupine seeds areextracted in an acid water extraction at pH values between 3 and 6, withno chemical reactions occurring between the solvent water and thedissolved lupine seed fractions. Various separation processs can be usedfor the actual separation between the solid parts, the so-calledraffinate I and the liquid part, the extract I, such as for exampleusing a decanter, separator or a filter. Also suited for separation is acontinuously operating drum centrifuge. The raffinate I obtained in thisseparation is then extracted using alkalized water at pH values of 7 to10 and divided following renewed solid-liquid separation into an extractII and a raffinate II. In this case too, separation occurs using thestate of the art separation process. The liquid extract II obtained inthe second separation step is acidified to a pH value between 3 and 5.5by adding an acid in doses due to which the predominant part of theproteins in the liquid extract II is precipitated. Acidification yieldsas the precipitant a precipitated protein in the form of a protein curdand excess liquid.

[0021] The excess liquid obtained by precipitation is then separatedfrom the protein curd in a further solid-liquid separation, for exampleusing a continuously operating drum centrifuge, thereby yielding liquidwhey with a protein content of 85% to 95% in dry substance.

[0022] The whey yielded in this manner is then undergoes to a membraneseparation process preferably by way of ultrafiltration with the targetproduct, notably the protein preparation, with the desiredpH-value-independent functional properties corresponding to the part ofthe whey retained by the membrane, the residue. The membranes used inthe ultrafiltration usually have pores which permit particles up to 10000, 20 000 or 50 000 dalton (D) to pass. In this manner, highermolecular constituents such as the desired proteins having molecularweights from up to 200 000 D remain as residue.

[0023] The residue yielded in this manner is predominantly composed ofthe desired high-molecular proteins, whose purity may be optionallyfurther improved by the residue undergoing a subsequent washing step.Suited for this additional washing step is conducting diafiltration inwhich the present high molecular protein is continuously or periodicallywashed, preferably in a multistage process, with water or a suitedbuffer solution. After corresponding drying, for example by spraydrying, a high-molecular, protein preparation of highest purity isproduced which possesses the properties mentioned in the introduction.The liquid parts, which essentially are composed of low-molecularconstituents such as sugar, salts, amino acids and peptides, separatedin the diafiltration can either be discarded as waste water or befurther processed for selectively obtaining individual substances.

[0024] As an alternative to conducting ultrafiltration of the wheyobtained by means of the above described solid-liquid separation, thewhey can also be upgraded by means of evaporation yielding a concentratewhich, after corresponding drying, preferably spray drying, alsocorresponds to a high-molecular protein with the desired functionalproperties.

[0025] The protein preparation producible using the aforedescribedvariant 1 has a very high sulfurous amino acid content and is thereforeparticularly suited for nutritional applications, for example additivesto baby food, health food products as well as for hospital food.Furthermore, the protein preparations possess especially good foamformation properties surpassing the foam volume values of commonproducts threefold.

[0026] Variant 2:

[0027] As in variant 1, the comminuted and faculatively deoiled lupineseeds undergo an aqueous extraction at pH values from 3 to 6 and arethen separated in solid-liquid separation into a raffinate and anextract. In contrast to variant 1, the liquid extract is selectivelyfurther processed. It immediately undergoes a membrane separationprocess, for example ultrafiltration, in which the protein preparationwith the desired functional properties is already obtained as residue,thus that very constituent that is retained by the membrane utilized inthe membrane separation process. As the residue has, despiteultrafilitration, only about a protein content in dry substance of 50%,the concentration of the high-molecular protein preparation can beincreased in the whey present as residue by washing the residue byconducting diafiltration. Preferably water is employed as the washliquid. By drying, preferably spray drying the washed residue, possiblyin conjunction with fluidized bed treatment, the protein can be obtainedas a dry product with suited particle packing.

[0028] The protein preparation produced in this manner is particularlydistinguished by it especially good solubility in a very broad pH range.The liquid parts separated in the diafiltration essentially containwater as well as low-molecular constituents such as sugar, salts, aminoacids and peptides, which can be discarded in the form of waste water orfurther processed in order to obtain single substances.

[0029] Variant 3:

[0030] The third alternative variant for producing a high-molecularprotein preparation with the desired functional properties, inparticular with regard to their good solubility, foam formation andemulsification over a broad pH range between pH 3 to pH 5 is acombination of the variants 1 and 2 described in the preceding.Accordingly, the whey produced in variant 1, which is obtained from theexcess liquid by means of solid-liquid separation, is selectivelyutilized as the wash liquid instead of water when conducting thediafiltration in variant 2. The use of whey as the wash liquid yieldsadvantages with regard to the water content of the entire process,thereby permitting raising efficiency respectively effectivity.Moreover, the protein preparations produced in this manner possessfunctional properties corresponding to those produced with variant 1 aswell as with variant 2.

[0031] Variant 4:

[0032] In contrast to the preceding variants 1 to 3, the comminuted andfacultatively deoiled lupine seeds undergo aqueous extraction atalkaline pH values from 7 to 10. The liquid extract obtained followingsolid-liquid separation undergoes precipitation by means ofacidification to pH values between 3 and 5.5, for example by addition ofsulfuric or hydrochloric acid, in which the major part of the proteinscontained in the liquid extract is precipitated. The excess liquidyielded in the precipitation is separated by means of solid-liquidseparation preferably with the aid of a decanter, thereby yielding theso-called whey. The proteins dissolved in the whey are then obtained inthe residue with the aid of a membrane separation process, preferablyusing ultrafiltration. The residue is predominantly composed ofhigh-molecular proteins which possess the aforedescribed properties. Asin the aforedescribed variants, in this case too the residue yielded byultrafiltration can also be washed with the aid of diafiltration usingwater as a washing liquid to further increase the concentration. Withinthe scope of the subsequent spray drying process, high-molecular proteinpreparations, for example with a solubility of more than 80% over abroad pH range, can in this way be produced in a technically efficientmanner.

[0033] Protein preparations produced by means of the four aforedescribedvariant methods show very good solubility in water in theapplication-relevant pH range (pH 2 to 12).

[0034] The extraction steps and the solid-liquid separation processes,in which water is preferably used as the solvent, are preferablyconducted at temperatures between 5 and 70° C., with temperatures from15 to 60° C. being especially suited. The addition of water as thesolvent for the extraction occurs in such a manner that a solid-liquidratio between 1:3 to 1:15 is yielded, with the preferred ratio beingbetween 1:4 and 1:10.

[0035] Fundamentally, the ultrafiltration may occur at pH values between3.5 and 9, the preferred pH values lying between 6 and 8 pH. Prior tocarrying out the ultrafiltration, the to-be treated whey can bepreferably pasteurized or undergoes high-temperature treatment. Typicaltemperatures for conducting the ultrafiltration lie between 10° C. and80° C., preferably between 60° C. to 80° C. In addition, the membranesused in the ultrafiltration possess selecting membrane apertures throughwhich the particles with molecular sizes of 100 000 D can permeate.

[0036] The protein preparations produced with the aforedescribedvariants methods all have a protein content of >80% in dry substance,preferably >85%. Their salt content is usually 3% to 5%. In the case ofextractive deoiling of the raw material, the fat content of the producedpreparation is under 1%, with the protein preparations produced by meansof variant 2 having a particularly low fat content.

[0037] Due to the especially favorable functional properties, inparticular with regard to their solubility, thermostability,emulsifiability, foam formation and gel formation, whose behavior isconstant practically over the entire pH range, the new high-molecularprotein preparations are suited for numerous important applications.Thus, they serve as additives for the following products; foams, gelsand gel-like substances, foods, beverages, feeds and cosmetic productsand technical products such as adhesives, pasty lubricants, paints etc.Employing the new protein preparations permits selectively adjusting thefunctional properties of individual products, for example with regard totheir solubility, emulsifiability, thermostability, foam formation andgel formation.

[0038] Finally, due to their high proportions of sulfurous amino acids,the new proteins, in particular those produced with the aid of variantmethod 1, permit derivation, i.e. the conversion into certain proteincompounds that are especially suited for special applications, whichoffer a wide spectrum for producing further new modified preparations.

What is claimed is:
 1. A method for producing protein preparationshaving essentially constant functional properties for technicalapplications within a broad pH range from about pH 3 to pH 10 by meansof extraction from a starting product which contains protein, notablylegumes, grains or oilseeds, characterized by the following processsteps: a) comminution of the starting product and addition of saidcomminuted starting product to a first acidic solvent at temperaturesbetween 5 and 70° C. in order to obtain an acidic suspension, b)separation of said acidic suspension into a raffinate I and an extract Iby way of solid/liquid separation, c) separation of said extract I usinga membrane separation process in order to obtain a residue containingthe protein preparations having the desired properties.
 2. The methodaccording to claim 1, wherein ultrafiltration is utilized as saidmembrane separation process.
 3. The method according to claim 1 or 2,wherein said residue is washed with water.
 4. The method according toclaim 3, wherein said washing of said residue is carried out by means ofdiafiltration.
 5. The method according to claim 3 or 4, wherein saidwashed residue is spray dried.
 6. The method according to the genericpart of claim 1, characterized by the following process steps: a)comminution of the starting product and addition of said comminutedstarting product to a first acidic solvent at temperatures between 5 and70° C. in order to obtain an acidic suspension, b) separation of saidacidic suspension into a raffinate I and an extract I by way ofsolid/liquid separation, c) addition of said raffinate I to a basesolvent in order to obtain a base suspension, d) separation of said basesuspension into a raffinate II and an extract II by way of solid/liquidseparation, e) acidification of said extract II and precipitation of theproteins from said acidified extract II in the form of protein curd inorder to obtain an excess liquid, f) separation of said excess liquid byway of solid/liquid separation in order to obtain a whey having aprotein content of >80% in dry substance, g) addition of said whey tosaid residue, which is produced according to the process steps a to caccording to the characterizing part of claim 1, and said whey is usedas washing liquid within the scope of diafiltration, and h) washing theproteins having said desired properties obtained in said residue.
 7. Themethod according to claim 6, wherein said residue obtained by saidwashing is spray dried.
 8. The method according to one of the claims 6or 7, wherein said acidic suspension possesses a pH value between 3 and5.
 9. The method according to the generic part of claim 1, characterizedby the following process steps: comminution of the starting product andaddition of said comminuted starting product to a first alkaline solventat temperatures between 5 and 70° C. in order to obtain an alkalinesuspension, separation of said alkaline suspension into a raffinate IIIand an extract III by way of solid/liquid separation, precipitation ofthe proteins from said extract III by adding an acidic medium in orderto obtain an excess liquid, separation of said excess liquid by way ofsolid/liquid separation in order to obtain a raffinate III and a whey,separation of said whey by way of a membrane separation process, inparticular by ultrafiltation, in order to obtain a residue composedpredominantly of proteins, which contains the protein preparationshaving the desired properties or upgrading of said whey by means ofevaporation in order to obtain a concentrate which is dried and containsprotein preparations having the desired properties.
 10. The methodaccording to claim 9, wherein said whey is washed with water.
 11. Themethod according to claim 10, wherein said washing of said whey iscarried out by means of diafiltration.
 12. The method according to claim10 or 11, wherein said washed whey is spray dried.
 13. The methodaccording to one of the claims 1 to 12, wherein said starting productare lupine seeds, in particular L. albus, L. luteus, L. angustifolius orL. mutabilis.
 14. The method according to one of the claim 1 to 13,wherein ground, flocked, pelletized and/or shelled lupines or otherlegumes or grains or oilseeds are employed as said starting product. 15.The method according to one of the claims 1 to 14 wherein said startingproduct is deoiled.
 16. The method according to one of the claims 1 to15, wherein separation membranes having exclusion sizes in the rangebetween 500 and 200 000 D are utilized for said membrane separationprocess.
 17. The method according to one of the claims 1 to 16, whereinwater mixed with acidified or alkaline substances depending on the pHsetting is utilized as said solvent.
 18. The method according to one ofthe claims 1 to 17, wherein solid/liquid ratios of 1:4 to 1:10 aremaintained during said extractions.
 19. The method according to one ofthe claims 1 to 18, wherein a pH value between 6 and 8 is set duringsaid membrane separation process and a temperature between 60 and 80° C.is set during said membrane separation process.
 20. A proteinpreparation which is produced according to one of the methods accordingto one of the claims 1 to 19 and which possesses essentially constantfunctional properties for technical applications within a broad pH rangeof about pH 3 to pH
 10. 21. The protein preparation according to claim20, wherein said protein preparation possesses a gamma-conglutinincontent of at least 30%.
 22. The protein preparation according to claim20 or 21, wherein said functional properties for technical applicationsare solubility, thermal stability, emulsifiability, foam formationand/or gel formation.
 23. The protein preparation according to one ofthe claims 20 to 22, wherein said protein preparation possesses asulfurous amino acid content of at least 2.0% w/w.
 24. The proteinpreparation according to one of the claims 20 to 23, wherein saidprotein preparation possesses an average molecular weight of at least100 000 D.
 25. The protein preparation according to one of the claims 20to 24, wherein the protein content in dry substance is between 60 and95%.
 26. Use of the protein preparation according to one of the claims20 to 25 or produced with one of the methods 1 to 23, as additive in k)gel or gel-like substance l) food and beverages m) feeds n) cosmetics o)paints p) adhesives q) rubber mixtures, plastic (thermoplastic)compounds, foam rubber, r) coatings for paper and plastics, expandedplastics, s) matrix binders for paper, composites, t) foams to achievethe functional properties for technical applications, such assolubility, emulsifiability, thermal structure stability, foamformation, or gel formation or Theological properties, such as liquidlimit, melting behavior, gliding properties, adhesive properties.